well they do really convert to 1080p. i mean your tv will receive 1920 x 1080 resolution as long as your tv is capable but the dvd player is effectively line doubling and guessing to fill in the blanks. not all upconversion chips are created equal either.
picture looks better than 480p for sure but dont expect to see jesus. if you need a dvd player buy and upconverting dvd player. if you already have one stick it out with that one till you go bluray.